The short half-life of carbon-11 excludes synthetic methods that are time-consuming. Rapid synthesis making use of reactive species generated by microwave activation, photolysis, high temperature techniques, and catalysis becomes the preferred technique for 11C-labeling. By these methods 11C-labeled precursors such as 11CH3I, 11CH3Li, H11CHO, and 11C2H2 can be prepared in a continuous and practical manner directly from (11C) methane, produced in a nitrogen and hydrogen (1-5%) mixture by proton bombardment. Availability of (11C) methyl lithium and (11C) ethinyl sodium allows 11C-labeling of many drugs that cannot be so marked otherwise. 11C-labeled benzene, chlorinated acetylenes, steroids, and others will be prepared for study in animals and man.